#include<iostream>
using namespace std;
const double PI=3.14159;
#include<math.h>
class Point 
{
    private :
	    double x,y;
	public:
	    Point();
	    Point(double a,double b);
    	double GetX() const;
	    double GetY() const;
    	void Change(double a,double b);
};
Point::Point()
{
	x=0;
	y=0;
}
Point::Point(double a,double b)
{
	x=a;
	y=b;
}
double Point::GetX()const
{
	return x;
}
double Point::GetY()const
{
	return y;
}
void Point::Change(double a,double b)
{
	x=a;
	y=b;
}
double Area(Point A,Point B)
{
	double len,area;
	len=sqrt((A.GetX()-B.GetX())*(A.GetX()-B.GetX())+(A.GetY()-B.GetY())*(A.GetY()-B.GetY()));
	area=PI*len*len;
	return area;
}
int main()
{
	const Point p1;
	Point p2(-5,3);
	cout<<"s1="<<Area(p1,p2)<<endl;
	p2.Change(56,34);
	cout<<"s2="<<Area(p1,p2)<<endl;
	return 0;
}
